import java.util.Scanner;

public class Main1603 {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int x=sc.nextInt();
        int y=sc.nextInt();
        double z=(x-1)*2.5+y*1.5;
        System.out.println(String.format("%.1f",z));
    }
}
